Jim Avery, the man responsible for keeping the lights on in San Diego, says he likes solar power.

As senior vice president of power supply for San Diego Gas & Electric, he was showing off two innovative technologies last week for turning sunlight into electricity. One uses the heat of the sun to run a helium-filled engine. The other concentrates rays onto tiny but highly efficient photovoltaic panels.

Avery, an electrical engineer, touted solar’s promise for providing a big chunk of the region’s power supply without producing greenhouse gases.

It’s a significant goal. California utilities are under a requirement to provide a third of the power they deliver to customers from renewable sources like solar, wind, geothermal and methane from rotting garbage and sewage.

For Avery, however, this isn’t simply a target to aim for. As the guy who has to crunch the numbers and make sure SDG&E has enough power to meet the needs of its customers and the requirements of regulators, the requirement is a goal he has to hit.

He has signed contracts for power from big desert plants, such as one near El Centro that plans to cover 10 square miles of desert with 30,000 dishes outfitted with generators — they’re called Stirling engines — to provide 750 megawatts.

Avery doesn’t mind taking on environmentalists to do his job. He’s spent much of the past decade advocating for the Sunrise Powerlink, a proposed 1,000-megawatt transmission line connecting the Imperial Valley to San Diego.

SDG&E says Sunrise will help bring power from renewables. Critics say it’s too big a fire risk, will spoil pristine landscapes and isn’t needed for San Diego to meet its goals.

San Diego is bathed in sun, particularly the eastern reaches of its suburbs, said Sunrise critic Bill Powers, an electrical engineer who said the region has the capacity to produce the renewable power SDG&E needs to meet its requirements.

“Is the solar intensity in the desert so much greater that the same panels sitting on a rooftop in El Cajon would produce power at twice the cost?” Powers asked, touting the idea of building small solar farms near users, rather than the massive desert farms SDG&E is counting on.

But as Avery showed off the technology that could go into the smaller, closer solar plants, he said the region doesn’t have a choice between the big desert farms and local generation.

“One of the misconceptions is that we could do this instead of that. We need to do it all,” he said. That’s because SDG&E has to plan for 5,000 megawatts of power to customers on the hottest summer day, and that power can’t all be made here.

QUESTION: What’s the potential for generating power in San Diego?

ANSWER: As I look at that 5,000 megawatts, we get a little bit less than 20 percent of that from our nuclear plant. We’re targeting to get about 33 percent from renewable sources, and the balance, another 45 to 50 percent, will be coming from natural gas resources, predominantly. If I look at that 33 percent, I look at where will we get that resource from. That will be made up of a mix of biomass, biogas that we have right now, like landfill gas sites, some geothermal resources, some wind resources and solar resources. Right now in San Diego, we have a little bit less than 80 megawatts sitting on rooftops. …

Now your question of how much (renewable power) can come from within San Diego. I believe a percentage of it can, but it’s not going to be the lion’s share of it. It’s going to be a relatively small share. … The amount of land that would be required with any of these technologies, Stirling or any of these solar technologies, to get the kind of power that could come across the Sunrise Powerlink, you need 10 square miles of land. Well, the relative cost of land out in the desert is a fraction of the cost that it would be in San Diego. Now we can put solar panels on rooftops, and we are doing that … I suspect there’s the potential to do well over 100 megawatts. But if you look at our resources, we need a couple of thousand megawatts. …

One of the things that’s critical to us is not just the energy, it’s the capacity. Those rooftop solar panels that sit up there, at 4 o’clock in the afternoon in late August, they’re producing a very small fraction of what they produce at noontime in mid-June.

QUESTION: Why?

ANSWER: To produce the optimum amount of energy, and you think about, if you’re going to make the investment to put solar panels on your roof, you want to get the most energy out, you have to really have those panels facing south and you want to tilt them somewhere between 17 and 18 degrees. Well, that is going to be producing the most amount of power at noontime (in June) when the sun is basically pointing directly at that same angle. When you get to late August, and the sun is sitting up here, so energy is reflected off the panels, it’s not fully consumed. … So we’re worried about the capacity, not just the energy.

(He points to the systems SDG&E is demonstrating.) These systems track the sun. … They are giving us much more capacity when we need it, which is why we think this is a critical part of our future.

QUESTION: The critics of Sunrise Powerlink say we don’t need it because we can make that power here. And this seems to be pointing that you can. You’re looking into making that power here?

ANSWER: What I think you’re missing out of the equation is that we need both. We’ve said from the beginning that we need every bit of this that can be developed here in San Diego, but we also need the large-scale projects we can develop in the desert. It’s not one or the other, we need both. … If you look at the solar dish here, any kind of cloud or haze, and that thing shuts down, there’s no power produced at all. Here, (pointing to concentrating photovoltaic array) a very thin cloud, these clouds right here, they probably cut production down by 80 percent, 90 percent. A thicker cloud shuts this one down completely as well.